As described, for example, in Patent Document 1, there is a device that is placed beside the track of a train and that is configured to detect the position of the train upon receiving a specified electric wave from a stationary wireless apparatus that radiates such an electric wave. This device is that which detects reaching a specified position of a train car according to a difference between a Doppler frequency of the electric wave received by an antenna placed at the front of the car and a Doppler frequency of the electric wave received by an antenna placed at the rear of the car.